Recently, with improvement of an information processing technology and development of an Internet environment, a required information processing volume has increased. This trend has been accompanied by taking attention on data center business that installs and runs apparatuses such as server apparatuses used for the Internet, communication apparatuses, fixed telephones, or IP (Internet Protocol) telephones.
A number of electronic devices such as computers are installed in a server room of the data center. As a method for installing electronic devices in a server room, a method using a rack-mount method is the mainstream. The rack-mount method is a method for installing by stacking flat electronic devices standardized according to JIS (Japanese Industrial Standards) or EIA (Electronic Industries Alliance) on a rack.
To secure sufficient space in a server room, as many electronic devices as possible are desirably mounted on a rack. Thus, it is desirable to lower the height of each electronic device. The height of an electronic device such as a 1 U (Unit) server or a blade server, referred to as a rack-mount server, is generally about 40 millimeters. To cool heat discharged from a rack-mount server, it is necessary to simultaneously cool a plurality of stacked heat sources having different height.
A cooling technology of the heat discharged from a rack-mount server is disclosed in, for example, Patent Literature 1. The Patent Literature 1 discloses a technology for cooling servers having different height arranged in respective server rooms of two floors, upper and lower, by using a boiling cooling method. An evaporator and a temperature sensor are arranged near an outlet of each of servers installed in the server rooms of the upper and lower floors. A refrigerant evaporated in each evaporator is cooled in a condenser disposed outside the server rooms to be condensed, and then flows again into the evaporator.
In a cooling apparatus of the Patent Literature 1, after a measurement temperature measured by each temperature sensor has been input to a controller, the controller controls an opening of a flow rate adjustment valve disposed in each evaporation unit based on the measurement temperature. Accordingly, refrigerants of appropriate flow rates for setting exhaust air temperatures to be equal can be supplied to each of the evaporators of the upper and lower floors with different height. As a result, the exhaust temperature of air discharged from the server room to the evaporator can be adjusted to a temperature environment suited for operating servers, and degradation of cooling performance caused by a shortage of a refrigerant flow rate can be suppressed.